/* * Lockless get_user_pages_fast for sparc, cribbed from powerpc * * Copyright (C) 2008 Nick Piggin * Copyright (C) 2008 Novell Inc. */#include<linux/sched.h>#include<linux/mm.h>#include<linux/vmstat.h>#include<linux/pagemap.h>#include<linux/rwsem.h>#include<asm/pgtable.h>/* * The performance critical leaf functions are made noinline otherwise gcc * inlines everything into a single function which results in too much * register pressure. */staticnoinlineintgup_pte_range(pmd_tpmd,unsignedlongaddr,unsignedlongend,intwrite,structpage**pages,int*nr){unsignedlongmask,result;pte_t*ptep;if(tlb_type==hypervisor){result=_PAGE_PRESENT_4V|_PAGE_P_4V;if(write)result|=_PAGE_WRITE_4V;}else{result=_PAGE_PRESENT_4U|_PAGE_P_4U;if(write)result|=_PAGE_WRITE_4U;}mask=result|_PAGE_SPECIAL;ptep=pte_offset_kernel(&pmd,addr);do{structpage*page,*head;pte_tpte=*ptep;if((pte_val(pte)&mask)!=result)return0;VM_BUG_ON(!pfn_valid(pte_pfn(pte)));/* The hugepage case is simplified on sparc64 because * we encode the sub-page pfn offsets into the * hugepage PTEs. We could optimize this in the future * use page_cache_add_speculative() for the hugepage case. */page=pte_page(pte);head=compound_head(page);if(!page_cache_get_speculative(head))return0;if(unlikely(pte_val(pte)!=pte_val(*ptep))){put_page(head);return0;}if(head!=page)get_huge_page_tail(page);pages[*nr]=page;(*nr)++;}while(ptep++,addr+=PAGE_SIZE,addr!=end);return1;}staticintgup_huge_pmd(pmd_t*pmdp,pmd_tpmd,unsignedlongaddr,unsignedlongend,intwrite,structpage**pages,int*nr){structpage*head,*page,*tail;u32mask;intrefs;mask=PMD_HUGE_PRESENT;if(write)mask|=PMD_HUGE_WRITE;if((pmd_val(pmd)&mask)!=mask)return0;refs=0;head=pmd_page(pmd);page=head+((addr&~PMD_MASK)>>PAGE_SHIFT);tail=page;do{VM_BUG_ON(compound_head(page)!=head);pages[*nr]=page;(*nr)++;page++;refs++;}while(addr+=PAGE_SIZE,addr!=end);if(!page_cache_add_speculative(head,refs)){*nr-=refs;return0;}if(unlikely(pmd_val(pmd)!=pmd_val(*pmdp))){*nr-=refs;while(refs--)put_page(head);return0;}/* Any tail page need their mapcount reference taken before we * return. */while(refs--){if(PageTail(tail))get_huge_page_tail(tail);tail++;}return1;}staticintgup_pmd_range(pud_tpud,unsignedlongaddr,unsignedlongend,intwrite,structpage**pages,int*nr){unsignedlongnext;pmd_t*pmdp;pmdp=pmd_offset(&pud,addr);do{pmd_tpmd=*pmdp;next=pmd_addr_end(addr,end);if(pmd_none(pmd)||pmd_trans_splitting(pmd))return0;if(unlikely(pmd_large(pmd))){if(!gup_huge_pmd(pmdp,pmd,addr,next,write,pages,nr))return0;}elseif(!gup_pte_range(pmd,addr,next,write,pages,nr))return0;}while(pmdp++,addr=next,addr!=end);return1;}staticintgup_pud_range(pgd_tpgd,unsignedlongaddr,unsignedlongend,intwrite,structpage**pages,int*nr){unsignedlongnext;pud_t*pudp;pudp=pud_offset(&pgd,addr);do{pud_tpud=*pudp;next=pud_addr_end(addr,end);if(pud_none(pud))return0;if(!gup_pmd_range(pud,addr,next,write,pages,nr))return0;}while(pudp++,addr=next,addr!=end);return1;}intget_user_pages_fast(unsignedlongstart,intnr_pages,intwrite,structpage**pages){structmm_struct*mm=current->mm;unsignedlongaddr,len,end;unsignedlongnext;pgd_t*pgdp;intnr=0;start&=PAGE_MASK;addr=start;len=(unsignedlong)nr_pages<<PAGE_SHIFT;end=start+len;/* * XXX: batch / limit 'nr', to avoid large irq off latency * needs some instrumenting to determine the common sizes used by * important workloads (eg. DB2), and whether limiting the batch size * will decrease performance. * * It seems like we're in the clear for the moment. Direct-IO is * the main guy that batches up lots of get_user_pages, and even * they are limited to 64-at-a-time which is not so many. *//* * This doesn't prevent pagetable teardown, but does prevent * the pagetables from being freed on sparc. * * So long as we atomically load page table pointers versus teardown, * we can follow the address down to the the page and take a ref on it. */local_irq_disable();pgdp=pgd_offset(mm,addr);do{pgd_tpgd=*pgdp;next=pgd_addr_end(addr,end);if(pgd_none(pgd))gotoslow;if(!gup_pud_range(pgd,addr,next,write,pages,&nr))gotoslow;}while(pgdp++,addr=next,addr!=end);local_irq_enable();VM_BUG_ON(nr!=(end-start)>>PAGE_SHIFT);returnnr;{intret;slow:local_irq_enable();/* Try to get the remaining pages with get_user_pages */start+=nr<<PAGE_SHIFT;pages+=nr;down_read(&mm->mmap_sem);ret=get_user_pages(current,mm,start,(end-start)>>PAGE_SHIFT,write,0,pages,NULL);up_read(&mm->mmap_sem);/* Have to be a bit careful with return values */if(nr>0){if(ret<0)ret=nr;elseret+=nr;}returnret;}}